Ecology of the Upper Jurassic brachiopod bed from Julianka, Polish Jura Chain

Abstract

Brachiopod bed in the uppermost Oxfordian chalky limestones from Julianka, Polish Jura Chain, is dominated by terebratulids that are to be considered as conspecific variants attributable to Sellithyris engeli (Rollier). The associated microfacies, distributional pattern of the fauna, and taphonomic analysis point to the autochthonous nature of the fossil assemblage. Most brachiopod species were displaying rapid early growth at the rate decreasing in ontogeny, and low early post-larval mortality at the rate increasing in ontogeny. The assemblage is to be interpreted as a pioneer, opportunistic one preceding the growth of coral patch-reefs. It includes species with habitat preferences for both inter-reef (Sellithyris engeli, Zeilleria delmontana, possibly also Septaliphoria moravica) and reefoid environments (Lacunosella cracoviensis, Septaliphoria astieriana, Terebratulina substriata).